In this paper we address radar-communication coexistence by modelling the radar environment as a Markov Decision Process (MDP), and then apply Deep-Q Learning to optimize radar performance. The radar environment includes a single point target and a communications system that will potentially interfere with the radar. We demonstrate that the Deep-Q Network (DQN) we construct is able to successfully avoid interfering with the communication system to improve its performance. We also show that the DQN method outperforms previous methods in terms of memory and handling new situations. In this thesis we also address the application of the MDP into a software defined radio (SDR) USRP X310 by utilizing the software LabVIEW to communicate with and control the SDR. / Master of Science / In this thesis we develop methods for creating and implementing algorithms for a cognitive radar. A cognitive radar is a radar that is able to sense its environment and avoid any other communication system that may interfere with its operation. We discuss the predictive methods we used to sense and avoid the other communication systems as well as how we implemented this using a software defined radar based on the USRP X310.

Software-defined radios have the agility and flexibility to tune performance parameters, allowing them to adapt to environmental changes, adapt to desired modes of operation, and provide varied functionality as needed.  Traditional software-defined radios use a combination of conditional processing and software-tuned hardware to enable these features and will critically sample the spectrum to ensure that only the required bandwidth is digitized.  While flexible, these systems are still constrained to perform only a single function at a time and digitize a single frequency sub-band at time, possibly limiting the radio's effectiveness. Radio systems commonly tune hardware manually or use software controls to digitize sub-bands as needed, critically sampling those sub-bands according to the Nyquist criterion.  Recent technology advancements have enabled efficient and cost-effective over-sampling of the spectrum, allowing all bandwidths of interest to be captured for processing simultaneously, a process known as band-sampling.  Simultaneous access to measurements from all of the frequency sub-bands enables both awareness of the spectrum and seamless operation between radio applications, which is critical to many applications.  Further, more information may be obtained for the spectral content of each sub-band from measurements of other sub-bands that could improve performance in applications such as detecting the presence of interference in weak signal measurements. This thesis presents a new method for confirming the source of detected energy in weak signal measurements by sampling them directly, then estimating their expected effects.  First, we assume that the detected signal is located within the frequency band as measured, and then we assume that the detected signal is, in fact, interference perceived as a result of signal aliasing.  By comparing the expected effects to the entire measurement and assuming the power spectral density of the digitized bandwidth is sparse, we demonstrate the capability to identify the true source of the detected energy.  We also demonstrate the ability of the method to identify interfering signals not by explicitly sampling them, but rather by measuring the signal aliases that they produce.  Finally, we demonstrate that by leveraging techniques developed in the field of Compressed Sensing, the method can recover signal aliases by analyzing less than 25 percent of the total spectrum. / Master of Science

Spectrum sharing is possible, but lacks R & D support for practical solutions that satisfy both the incumbent and secondary or opportunistic users. The author found a lack of an openly available framework supporting experimental research on the performance of a Spectrum Access System (SAS) and propose to build an open-source Software Defined Radio (SDR) based framework. This framework will test different dynamic spectrum scenarios in a wireless testbed. This thesis presents our Spectrum Access System prototype, discusses the design choices and trade-offs and provides a proof of concept implementation. We show that an Internet-accessible CORNET test bed provides the ideal platform for developing and testing the SAS functionality and its building blocks and offerss the hardware and software as a community resource for research and education. This design provides the necessary interfaces for researchers to develop and test their SAS-related modules, waveforms and scenarios. / Master of Science / In this information age, the number of wireless devices is growing faster than the infrastructure required to make wireless communication possible. This creates a possibility of not having enough radio spectrum to keep up with this growing demand. To alleviate this issue, there is a need to research and find more ways of efficiently utilizing the current spectrum resources available. Dynamic spectrum allocation is one way forward to archiving this goal. Frequency channels are assigned to devices based on prevailing conditions like device location and availability of channels that would cause low interference to other devices. Spectrum utilization is based on time, frequency and space with devices having the ability to hop to the best channel available. In this thesis, an open-source Spectrum Access System (SAS) was created as a platform through which dynamic spectrum allocation research can be done. The SAS is centralized management system that logs information about the prevailing spectrum usage, and in turn uses this information to dynamically allocate spectrum to devices and networks. This thesis shows how it was implemented, its current performance, and the steps that different researchers can take to add their own functionalities.

Yes / The redesign of defined benefit pension schemes usually results in a substantial redistribution of wealth between age cohorts of members, pensioners, and the sponsor. This is the first study to quantify the redistributive effects of a rule change by a real world scheme (the Universities Superannuation Scheme, USS) where the sponsor underwrites the pension promise. In October 2011 USS closed its final salary scheme to new members, opened a career average revalued earnings (CARE) section, and moved to ‘cap and share’ contribution rates. We find that the pre-October 2011 scheme was not viable in the long run, while the post-October 2011 scheme is probably viable in the long run, but faces medium term problems. In October 2011 future members of USS lost 65% of their pension wealth (or roughly £100,000 per head), equivalent to a reduction of roughly 11% in their total compensation, while those aged over 57 years lost almost nothing. The riskiness of the pension wealth of future members increased by a third, while the riskiness of the present value of the sponsor’s future contributions reduced by 10%. Finally, the sponsor’s wealth increased by about £32.5 billion, equivalent to a reduction of 26% in their pension costs. / The full text will be available at the end of the publisher's embargo; Oct 16 2017

Yes / Purpose Flicker-defined form (FDF) stimuli have recently been adopted for visual field testing. A key difference between FDF and traditional perimetric stimuli is that the entire display background contains flickering dots. The purpose of this study was to determine whether the perception of FDF stimuli is influenced by lateral interactions involving regions beyond the stimulus border in young healthy observers. Methods Experiment 1 measured the effect of surround size and retinal eccentricity on the detection of the FDF contour. Psychometric functions were collected for surround diameters of 20°, 30° and 40°, and with stimuli centred at eccentricities of 0°, 10° and 20°. Experiment 2 measured the effect of target-surround temporal phase difference on apparent temporal contrast (flicker strength) of the target for both the FDF stimulus and a solid-field stimulus. Psychometric functions were collected for target-surround phase differences of 0°, 45°, 90°, 135° and 180°. Results Our results show a mild surround-suppression effect for FDF stimuli that is independent of surround size. Magnitudes of FDF surround suppression were consistent with the reduced temporal contrast energy of the stimulus compared to solid-field stimuli. Conclusion FDF stimuli necessarily have both flickering target and background. Our results suggest that visual field defects outside the target are unlikely to markedly influence the detection and perception of the FDF stimulus. Nevertheless, mild surround suppression of contrast arises for FDF stimuli, hence interactions between the background and the target area may influence FDF results in conditions that alter centre-surround perceptual effects.

Increasing interest in ultra-wideband (UWB) communications has engendered the need for a test bed for UWB systems. An FPGA-based software-defined radio provides both post-fabrication definition of the radio and ample parallel processing power. This thesis presents the FPGA design for a software-defined radio targeted to impulse ultra-wideband signals. The system is capable of an effective sampling frequency of up to 8 G-samples/s using time interleaved sampling with eight 1-GHz ADCs. The system is also capable of transmitting UWB pulses using a transmitter board controlled by the FPGA. In this thesis, the FPGA design used to capture and export data from the eight ADCs is presented, along with two systems which make use of the transceiver: a pilot-based matched filter communications system, and a remote vital signs monitor. / Master of Science

The Global System for Mobile (GSM) cellular standard, having been in existence for over two decades, is the most widely deployed wireless technology in the world. While third generation networks and beyond, such as Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE), are undergoing extraordinary growth and driving a large share of current cellular development, technologies and deployments based on GSM are still dominant on a global scale and, like more recent standards, continue to evolve very rapidly. The software-defined radio (SDR) base station is one technology that is driving rapid change in cellular infrastructure. While commercial vendors have now embraced SDR, there is another movement that has recently gained prominence. That movement is the convergence of open source software and hardware with cellular implementation. OpenBTS, a deployable implementation of the GSM radio air interface, and the Universal Software Radio Peripheral (USRP), a RF hardware platform, are two primary examples of such open source software and hardware products. OpenBTS and the USRP underlie three GSM features that are implemented and presented in this thesis. This thesis describes the extension of the OpenBTS software-defined radio transceiver in the three critical areas of user capacity, transmit signal integrity, and the embedded small form factor. First, an optimized wideband multicarrier implementation is presented that substantially increases the capacity beyond that of a single carrier system. Second, the GSM modulator is examined in depth and extended to provide performance that exceeds standards compliance by a significant margin. Third, operation of the GSM transceiver on an E100 embedded platform with ARM and fixed point DSP processors will be explored, optimized, and tested. / Master of Science

The advent of software radio technology has enabled radio developers to design and implement radios with great ease and flexibility. Software radios are effective in experimentation and development of radio designs. However, they have limitations when it comes to high-speed, high-throughput designs. This limitation can be overcome by introducing a hardware element to the software radio platform. Enhancing GNU Radio for Hardware Accelerated Radio Design project implements such a scheme by augmenting an FPGA co-processor to a conventional GNU Radio flow. In this thesis, this novel platform is evaluated in terms of performance of a radio design, as well as hardware and software system requirements. A simple and efficient Zigbee receiver design is presented. Implementation of this receiver is used as a proof-of-concept for the effectiveness and design methodology of the modified GNU Radio. This work also proposes a scheme to extend this idea for design of ultra-wideband radio systems based on multiband-OFDM. / Master of Science

我國65歲以上的老年人口，於民國82年底達總人口比率7.1％，正式邁入聯合國世界衛生組織所稱之高齡化社會（7％以上）。根據行政院經濟建設委員會之推估，65歲以上的老年人口比例於97年將達總人口數之10.15％，而於116年達總人口數之20.04％，人口老化速度明顯高於歐美國家，未來人口年齡結構將更趨於高齡化。隨著我國老年人口成長，社會安全制度日益受到重視，提供老人經濟安全之適度保障將成為我國未來福利發展之新方向。 本研究根據世界銀行提出的「三層保障」之老年經濟安全保障制度架構為基礎，說明我國公務人員退休制度在老年經濟安全保障方案之定位，闡述有關第二層保障之職業退休金制度理論演變，以釐清公務人員退休金之屬性及正當性，以助於退休制度及其財務規劃的擬定，期使整套制度循著適當的理論脈絡而發展。基於對退休金重要性的認知，先進國家早已發展成熟的職業退休金制度，而我國公務人員退休制度係建制於民國32年，實施50餘年，雖歷經4次修正，由於退休金給付方式仍屬於恩給制，除造成財政上重大負擔外，也產生退休給與偏低等嚴重問題，相關機關自62年開始研究改革，經過22年研議規劃完成，自84年7月1日實施退休新制，其與舊制最大的差異，是將退休經費籌措方式，由政府編列預算支付之恩給制，改由政府與公務人員共同撥繳費用成立退撫基金之共同提撥制，其餘退休對象、退休年資、退休條件、核給退休金原則大致維持不變，而退休金給付方式，也維持著確定給付制。經分析新退休制度之主要內容，實施迄今8年餘，有關改進退撫經費籌措方式，減輕政府財政負擔；及提高退撫所得，加強安老卹孤之改革目標，均已獲致初步成效。然而現階段面臨之問題，是退休經費導致各級政府財政負擔增加，且依公務人員退休撫卹基金管理委員會委託基金精算結果也顯示基金將面臨財務危機。 本研究係分析新制退休金給付方式，全面採行確定提撥制，對解決基金現存財務危機之可行性，為便於瞭解，爰敘明確定提撥制與確定給付制之意涵與優、缺點，及我國採用此兩種制度之適例。茲因退休金給付方式之政策變革方案，影響層面甚廣，方案之可行性如何，必須審慎探討與分析，爰就制度變革方案可行性列舉幾項評估面向進行分析。 例如為解決基金財務問題，除必須從經濟上分析外，茲因制度變革方案，必須符合現時的政治生態，始能確保政策推行之成果，方案的周詳與否，關係到該方案能否被接受及未來能否順利執行。由於退休舊制恩給制時期，因退休經費籌措方式不當，同樣存在著財政負擔之問題及缺失，其能於84年7月改革成功推動新退休制度，在政治方面包括政黨、民意機關、相關主管機關、公務人員，甚至學者等等支持的因素，在現今新制推行後，為解決財政問題，而將退休金給付方式，全面改採確定提撥制，是否同樣具有政治上支持的可能性，自須審慎分析；此外，退休金政策之改變，直接受影響的便是公務人員之退休所得，在退休金採行確定提撥制後，是否仍能達成新制推行時所設定之提高退撫所得、加強安老卹孤改革目標，應為關鍵之所在，由於職業退休金理論中之維持適當生活，係本研究在規劃退休金制度時所考量的重點，因退休後的生活水準應能與退休前相當，乃是探討退休金制度的核心，爰列為評估面向。又世界各國實施公務員退休金制度之經驗，包括採行確定給付制與確定提撥制例證，及面臨困境或改革之趨勢，均能在我國制訂退休金政策時有所啟示，故亦列為評估面向。本研究依據上述重要項目進行整體性評估，針對現存政經環境及職業特性，歸納我國新制退休金採行確定給付制或確定提撥制之個別效益，深入檢討何種給付方式較能維持公務人員權益？及退休前之生活水準？藉以說明並支持可行方案，以作為方案選擇之參據。最後提出本研究之結論與研究發現，進而本於基金能否永續經營，將是制度得否存續的關鍵，減少財務潛在危機，應具有合理的制度設計與有效的經營管理之基本條件，爰研擬若干建議措施，以降低財政問題的嚴重性，俾確保基金日後退休給付之能力，保障參加基金人員之權益。 / Taiwan has officially joined the “aging society” as defined by the WHO (up to 7% of the senior citizen ratio) because senior citizens aged over 65 accounted for 7.1% as of December 31, 1993. The official forecast by the Council of Economic Planning & Development of the Executive Yuan (the Cabinet) indicates that the senior population age over 65 will hit 10.15% of the total population by 2008 and even up to 20.04％ by the year 2027. Taiwan significantly outpaces their European and American counterparts in terms of the ratio of aging citizens. The aging society problems will likely turn from bad to worse in the future. In turn, the social security system is receiving mounting awareness and attention. The efforts to provide sound financial standing, secured social systems and protection to senior citizens will represent the new orientation of future welfare development in Taiwan. The present study takes the “Three-Level Assurance” oriented senior citizen financial security system proposed by the World Bank as the very grounds to elucidate the positioning of the Public Servant System in the senior citizen financial security system, annotate the evolution pension system of the Second-level Assurance to clarify the attribute and justification of the pension granted to civil servants. The present study is intended to help draw up a retirement system and financial planning so that the entire system will develop toward appropriate and justified orientation. With awareness of the importance of pension, those advanced countries have developed sound and mature professional pension systems for quite some time already. In the Republic of China, the retirement system for civil servants was initiated in 1943 and has been updated four times during the subsequent half century. The pension has been granted as a sort of benefit, or a government favor. As a result, pension to civil servants has become a heavy financial burden to the government and has been illogically insufficient. In response, the competent authorities concerned began initiating research for a reform of the pension system in 1973 and completed the research program 22 years later. The new retirement system was officially put into place on July 1, 1995. Between the old and new retirement system, the greatest difference is that the pension fund is jointly contributed by both the government and civil servants themselves in the new system instead of being solely budgeted by the government as a sort of government favor in the old system. Except for this, the aspects of the target retirees, seniority requirements, prerequisites for retirement and the principles to grant pension largely remain unchanged. Pension is paid in an unchanged “Defined Benefit Plan”. Now, with the new system in enforcement for over eight years, the new system proves to have primarily attained the goals in improving the method of pension fund raising, easing up the government’s financial burden, providing added pension to retirees and better safeguarding the senior civil servants. The problems currently confronting the pension practice are largely the mounting financial burden to the government as incurred by the retirement expenses. Meanwhile, the actual calculation outcome consigned by the Pension Management Committee indicates that the Pension Fund is on the verge of financial difficulties. The present study is to analyze the terms of pension payment to determine the feasibility there-of and to solve the present financial problem by means of the “Defined Contribution Plan”. For better a understanding into the issues, the present study elucidates the connotation, strengths and weaknesses of the “Defined Contribution Plan” and “Defined Benefit Plan”, as well as the precedents in Taiwan in adopting such two systems. Where a reform in the policy of pension payments will create quite an extensive impact, the feasibility of the policies calls for prudent analysis to enumerate a few feasible alternatives before further analyses into a few aspects of the assessment. To solve the financial difficulties in the Pension Fund, for instance, other than the economic analyses, the reform of the system must live up to the current political ecology before it can ensure the effects expected through the enforcement. Whether or not the policies are detailed and comprehensive enough will determine whether or not the policies are acceptable and whether or not they can be put into successful enforcement without a ensuing problems. During the extended practice under the old system while pension was budgeted as a sort of government favor, the pension system led to a heavy financial burden and shortcomings on the government. The new pension system was successfully put into enforcement in July 1995, thanks to the unanimous support from the political parties, congress, competent authorities concerned, civil servants as well as scholars. Now, in an effort to solve the current financial problems under the new system, the pension will be paid under the “Defined Contribution Plan”. Will the present reform receive equal political support? It calls for well-advised analyses. Besides, in a change in the pension system, the top impact will be upon the pension income to civil servants. After the pension is under the “Defined Contribution Plan”, will civil servants receive added pension income and receive better security in their retired life? These will be the key issues under the present study. The core consideration should aim at the retired lifestyle, which should be equivalent to the pre-retirement one. The hands-on experiences in enforcing civil servant pension systems accumulated in other countries the world over, including precedents of their practices in adopting the “Defined Benefit Plan” and “Defined Contribution Plan” will function as the constructive examples in Taiwan’s policymaking process regarding pension systems, and will be, therefore, be covered in the assessment in the present study as well. The present study will launch an overall assessment on the aforementioned key issues. Aiming at the existent political and economic climate as well as the professional characteristics, the present study will generalize the individual effects and benefits under “Defined Benefit Plan” or “Defined Contribution Plan” under the new retirement system to find out the optimal terms of payment to assure maximum possible benefits to civil servants, safeguard the quality of their retired lifestyle to be equivalent to the pre-retirement lifestyle. The findings and conclusions yielded through the present study will function as handy reference materials for policymaking. By submitting the findings and conclusions so yielded, the study will help the policymakers draw up sound enforcement rules to ensure the sustained existence of the Pension Fund, alleviate the potential financial crises through reasonable design of systems and effective management as the very fundamentals. Further by offering constructive proposals, the study will help the competent authorities of the government solve the financial difficulties to ensure sustained sound competence of pension payments and to, in turn, safeguard the Pension Fund and the Fund’s beneficiaries.

By the end of the twentieth century, the generous German public pay-as-you-go pension system had been struggling with a serious deficit due to the country’s ageing population. In 2001, the German government enacted the “Riester” pension reform, named after Mr. Walter Riester, the Labour Minister brokering it, which reduced the level of publicly provided pensions, and strengthened the funded occupational and private pillars in order to replace the loss in retirement income. This thesis investigates the role and structure of occupational pensions during the Riester-reform and in its aftermath, using an economic geography perspective. In doing so, it discusses the role of trade unions and employer associations (social partners) in moulding the structure of the occupational system, and investigates the geography of occupational pensions both at employer and at employee level. Empirically, the thesis is based on an in-depth interview with Mr. Walter Riester, and a unique, proprietary data-set of a German occupational pension provider, containing information on 332 thousand employees and over 12 thousand employers. The results show that the internal division of social partners played a critical role in leaving occupational pensions voluntary, but they have been successful in setting standards on the occupational pension market by means of collective bargaining. Employers and employees show systematic spatiotemporal patterns in their pension-related decisions, confirming the importance of local relationships and local contexts in implementing social partners’ measures and in the transformation of the welfare state. It is finally pointed out that the Riester-reform was a part of a gradual transition, which has been reducing employers’ autonomy in order to reinforce the social role of occupational pensions. To achieve that and to catalyse the reform process, employers’ and employees’ risk exposure has been mitigated in the hope that old-age poverty can be avoided.